In line water heater

In our new home we have a whirlpool tub. We have a 50 gallon water heater but it doesn't seem to be enough to fill the tub. I'd like to put in an in line instant water heater for the tub. We have good access to the mechanics and plenty of room for the heater. Since there are plug ins by the workings I'd like to use 110 instead of 220. Will that give me enough power to run the heater?
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gilmoreguy wrote:

No, say it is a 20A outlet. It can supply 16A max which is only 6,500 BTU/hr.
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At half the voltage, an appliance of the same wattage would require twice the current.
Try this. Run the hot water just long enough to get some in the tub, maybe 5-10 gal at the most. Now shut it off and wait for the water heater to finish reheating the water in the tank (this takes a fraction of the time it takes to heat the whole tank after filling the tub). Now you can finish filling the tub and have a little hot to spare.
Often when you decide to take a bath, the water in the tank is not really at its max temp (requireing you to use that much more). This procedure ensures the WH is completely full with max temp water and provides some in the pipes (if they are insulated) and the initial draw.

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heat. If you are just trying to increase the temperature of the water that comes from your existing water heater, that might be enough. But you will have to run a circuit for it anyhow; why not just run a 240v circuit?
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Fixed appliances require separate circuits. Anything attached to a tub in a bathroom should be on a gfci. Using a existing circuit is not the way to do it.
Raise the temp of the water heater.
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